Case 2 Data:
100% Mg recovery may be just over the horizon! REFERENCES
1. Ductile Iron Production Practices, Karsay, S.I., American Foundrymen’s Society, Inc Publication (1985).
2. Labrecque, C., Gagné, M., “Review Ductile Iron: Fifty Years of Continuous Development” Canadian Metallurgical Quarterly, vol.37, no.5 pp.343-378 (1998).
3. Millis, K.D., Gagnebin, A.P., Pilling, N.B., “Cast Ferrous Alloy”, US Patent 2,485,760 (1949).
4. Gußeisen; Piwowarsky, E., Springer-Verlag (1951). 5. Principles of Metal Casting; Heine, R.W., Loper, C., Rosenthal, P.C., Tata McGraw-Hill Edition 1976, ISBN 0-07-099348-3 (2005).
Summary
1) Lower Mg content alloys (5.9wt% Mg down to 4.1wt% Mg) have shown a self-compensating recovery effect, whereby the % Mg recovery increases to offset the lower Mg content. This allows the use of lower cost al- loy with reduced reaction violence and slag generation. These lower reactivity alloys are more suited for use in ladles used for simultaneous Mg treatment and inocula- tion. Those alloyed with pure La are preferred to mini- mize shrinkage issues.
2) Finding means to lower the treatment temperature is very important to gain large jumps in Mg recovery. Elimination of the treatment ladle where this is feasible is one way to achieve this. Converting the treatment ladle to a transfer ladle and doing the Mg treatment and inoculation simultaneously in the pouring ladle is an- other. Eliminating the quenching effect of steel cover can add to these gains.
3) Altering the timing of the MgFeSi reaction can have a major effect on Mg recovery. An ideal fill time is one that allows all the iron to be added into the ladle before the MgFeSi alloy starts to react, as opposed to reacting while the ladle fills. Means to achieve this are to fill very rapidly, as is possible with use of a transfer ladle with a pre-measured amount of iron. This allows the iron to be transferred to a ladle (used for treating and pour- ing) at the pouring area in a fraction of the time when compared to a slower furnace fill. Deeper alloy pockets extend the time before iron flows over into a pocket dur- ing filling. For the same amount of cover alloy, they provide a deeper barrier of cover alloy to delay the re- action. When an engineered cover-inoculant FeSi alloy is used, the barrier effect becomes more effective. For these improved pockets the release of Mg into the iron is controlled to a slower rate over a longer time, further enhancing recovery with an associated calmer reaction.
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6. Heine, H., “An Overview of Magnesium Treatment Processes Which Have Stood the Test of Time in America,” BCIRA Conference –
S.G.Iron The next 40 Years, Warwick, UK (1987).
7. Skaland, T., “Ductile Iron Production – A Comparison of Alternative Treatment Methods,” Metal Casting and Surface Finishing (1999).
8. Forrest, R.D., Wolfensberger, H., “Improved Ladle Treatment of Ductile Iron by Means of the Tundish Cover,” AFS Transactions, vol. 88, pp. 421-426 (1980).
9. Elkem presentations 10. Loper, C.R., Heine, R.W., Wang, C.C., Janowski, L., “Fading of Magnesium Treatment in Ductile Cast Irons,” AFS Transactions, vol. 84, pp. 203-214 (1976).
11. Dunks, C.M, “Process for Manufacturing of Cast Iron”, U.S. Patent 4,004,630,(1975).
12. Holden, W.W., Dunks. C.M., “The Practical Application and Economic aspect of the Inmold process in the United States,” British Foundryman, 73- 265 (1980).
13. Elkem Internal Report 24th October, 1994
14. Hoel, E.G., “Structures and phase relations in silicomanganese alloys” Phd Thesis Met. Inst, NTNU, 1998, MI-report 1998:52
15. Guichelaar, P.J, Trojan. P.K, McCluhan, T., Flinn, R.A., “A new technique for vapor pressure measurement applied to Fe-Si-Mg system”, Metallurgical and Materials Transaction, vol.2, no. 2, pp 3305-3313 (1971).
16. Colour Metallography of Cast Iron, Zhou, J., China Foundry, vol. 7, issue 3 (2010).
17. Morrogh, H., Williams, W.J., “The Production of Nodular Graphite Structures in Cast Iron” Journal of the Iron and Steel Institute (March 1948).
18. Hoel, E.G., Elkem Internal Report F173/08 (2008). 19. Elkem Internal Report STF34 F91045 (February 1991). 20. Schumacher, W., “Magnesiumvorlegierungen und deren Einbringen in Gußeisenschmelzen zur
International Journal of Metalcasting/Volume 8, Issue 2, 2014
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